1. Field of the Invention
The invention relates to an apparatus and method for controlling ignition timing during a shift in a vehicular automatic transmission, which temporarily reduces an input torque to the automatic transmission according to a required retard amount during a shift of the automatic transmission.
2. Description of the Related Art
Art relating to an apparatus for controlling the ignition timing during a shift in a vehicular automatic transmission is known which is provided with a torque-down controller, which i) determines a retard amount required to temporarily reduce a torque input from an engine provided with an ignition timing retard controller to an automatic transmission (hereinafter, referred to as “input torque”) based on an estimated input torque of the automatic transmission and a vehicle speed, and ii) temporarily reduces the input torque based on that determined retard amount during shifting of the automatic transmission. Because this type of control apparatus temporarily reduces the input torque to the automatic transmission during the shift period, shift shock is able to be preferably suppressed.
With this type of control apparatus, a preset relationship of the required retard amount with the estimated input torque of the automatic transmission and the vehicle speed is stored, and the retard amount corresponding with the actual estimated input torque and vehicle speed is determined in the same way. Therefore, if the output state of the engine changes due to a parameter other than the engine speed and a required load value used for calculating the estimated input torque, such as a throttle opening amount, an accelerator pedal operation amount, or an intake air quantity, shift shock is not able to be sufficiently reduced.
With respect to this, the following related art exists. This related art relates to a shift shock reducing apparatus for an automatic transmission, which is characterised in that it i) first calculates a difference between a shift time target value and an actual shift time, ii) determines a torque-down correction amount so as to eliminate that difference, and iii) sends a command to the engine to use the last torque-down amount corrected by the determined correction amount as the new torque down amount for the next shift. Because this shift shock reducing apparatus corrects the torque-down amount such that the actual shift time matches the shift time target value, shift shock is able to be preferably suppressed even if the input torque to the automatic transmission is affected by a change over time in the engine output characteristics or an external change such as a change in the fuel or air pressure or the like.
According to this shift shock reducing apparatus, however, because the torque-down correction amount is reflected in the next shift, it does not enable shift shock to be avoided during the first shift after the engine output characteristics change. Further, if the change in the engine output characteristics is large, shift shock will occur even if the torque-down correction amount is reflected in the next shift.